1. Field of the Invention
The present invention relates to an off-mains switch as well as a control box for an actuator system intended for use in connection with electrically driven articles of furniture.
2. The Prior Art
To avoid the situation that an electrically adjustable and/or driven article of furniture, such as a bed, a chair or a table, is constantly supplied with mains voltage to the local transformer of the article of furniture, so-called off-mains switches have been developed, which automatically interrupt the connection between the mains supply and the local transformer when the article of furniture is not active, i.e. is not adjusted. The interruption may take place by means of a relay, or a unit having a corresponding relay function, located in the off-mains switch.
When the article of furniture is adjusted to perform e.g. a raise function, such as by operation of a functional key on a hand control associated with the article of furniture, or by a separate activation of the off-mains switch via the hand control and/or directly on the off-mains switch, the off-mains switch is activated and establishes the connection to the mains. Such off-mains switches are known from EP 0 615 667 B2 Okin, DE 92 12 599.9 U1 Dewert, EP 0 792 532 B1 LINAK as well as WO 2004/019463 A1 LINAK. Off-mains switches serve inter alia to prevent or at least reduce the presence of electric or magnetic fields, E-fields and H-fields, respectively, in the article of furniture.
The off-mains switch of EP 0 615 667 is based on an actuator system, in which the operational voltage to the actuator is also a control voltage. Activation of the relay relies on the use of an auxiliary voltage source, coupled in parallel with the main power supply, in the form of a capacitor coupled in parallel with the power supply. The capacitor is supported by a battery in the event that the capacitor should lose its charge. In practice, it has been found that both capacitor and battery may run out of power, and therefore the realization of the invention additionally includes a push-button for manual activation of the relay.
In EP 0 792 533, the mains voltage is interrupted by a set of TRIACs instead of a relay. When the system is operated, the TRIACs are activated by an optocoupler which receives power from a high capacity capacitor, which is kept charged by being connected briefly to the mains at regular intervals. This is done via separate control electronics based on a timer. Another solution is based on a small auxiliary capacitor permanently connected to the mains via voltage-restricting means, and with just enough capacity to activate the optocoupler a single time. These, however, are relatively expensive solutions.
In the vast majority of examples, the electrically adjustable article of furniture is equipped with an actuator system, which may be consist of at least one actuator driven by a low volt DC motor, a control box which may comprise a main power supply having a transformer for feeding the motor, a rectifier and a smoothing capacitor, an electrical control unit and finally at least one hand control which may be a wired and/or be a fixed operating panel or a remote control for activating the control unit. The electrical control unit moreover comprises control of the function which the activator may make the article of furniture perform.
The off-mains switch is typically mounted in a plug box which is inserted into an outlet, and the outlet is most often located at an arbitrary distance from the article of furniture. A special cable, hereinafter called intermediate cable or mains cable, is run from the off-mains switch to the article of furniture. This intermediate cable contains a mains cable having two conductors for feeding the main power supply, and optionally an additional conductor for earth connection, as well as at least one additional wire having a conductor for use in the control of the relay in the off-mains switch by means of the control unit, which may result in a strong and inflexible total intermediate cable.
A special cable, like an intermediate cable, is relatively costly per se, and to avoid special connectors, which may also be relatively costly, the cable is firmly mounted in the off-mains switch as well as in the power supply and the control unit. This is not very expedient in terms of handling and shipment. In addition, a standard length of the intermediate cable also has to be used, more or less, irrespective of the customer's needs being a shorter or longer cable.
It may be seen as an object of the invention to provide an off-mains switch as well as a control box for an actuator system intended for use for an adjustable article of furniture, which fully or partly solves one or more of the above problems singly or in any combination.
It may be seen as an object of the invention to provide a structure and a mode of operation for an off-mains switch and a control box, coupled to it, for an actuator system, in which electric and/or magnetic fields at the actuator because of a mains voltage do not exist, and in which it is constantly ensured that energy is present at the actuator for establishing connection of the actuator to the mains voltage.
It may be seen as an object of the invention to provide a structure of an off-mains switch and a control box for an actuator system, where a single cable having two conductors as an intermediate cable will suffice, that is where the intermediate cable exclusively consists of a cable having two conductors and optionally an additional conductor for an optional earth connection.
When the signals between the control unit and the off-mains switch may be transmitted through a mains cable, a separate conductor for transmitting the control signal is not needed, and a standard mains cable having two electrical conductors as an intermediate cable suffices. This means in turn that a standard plug may be used, and thus the cable may be connected to the power supply via an ordinary plug. Since the off-mains switch may hereby appear as a separate unit, production and logistics will be facilitated.
When the control signal applied from the control box to the off-mains switch is used as an indicator of the size of the low energy storage in the control box, a solution is achieved where the off-mains switch and the control box currently exchange information on the size of the energy storage. Hereby, the amount of energy on the low energy storage may be adapted such that enough energy is constantly available for supplying the control signal transmitter—but such that as little energy as possible is transferred to the control box in a passive state.
When the size and/or the frequency of the low voltage and thereby the low energy transfer to the low energy storage are changed only when so needed because of declining strength and/or frequency and/or duration of the control signal, a solution is achieved where it is constantly ensured that there is energy in the control box during “passive mode” for applying a control signal to the off-mains switch, and where it is ensured at the same time that the amount of low energy being transferred is adapted to this purpose.
The invention also relates to an actuator system, which comprises the inventive off-mains switch and control box, the actuator system additionally comprising an actuator with an associated operating unit.
The invention moreover relates to a system of furniture consisting of an actuator system according to the invention, the system of furniture additionally comprising an electrically adjustable article of furniture whose adjustment may be controlled by the actuator.
Additional advantages will appear from the following detailed description.